Bobbin case for sewing machines



Oct. 20, 1942. D. H. CHASON BOBBIN-CASE FOR SEWING MACHINES Filed July 9, 1941 INVENTOR. ww/a m cm saw v Patented Oct. 20, 1942 UNITED STATES FATEI -IT OFFICE BOBBIN CASE FOR SEWING MACHINES Application July 9, 1941, Serial No. 401,580

1 Claim.

This invention relates to lock-stitch sewing machines and more particularly to bobbin-cases therefor and has for its objective the provision of improved means for preventing the thread from being inadvertently pulled from under the bobbin-thread tension spring when the bobbinthread is being pulled beneath the spring.

The several features of the present invention will be clearly understood from the following description and accompanying drawing in which:

Fig. 1 is a top plan view of a bobbin-case having my improved tension spring secured thereto.

Fig. 2 is a side elevation of the bobbin-case shown in Fig. 1.

Fig. 3 is a perspective view of my improved tension spring.

In the embodiment of the invention selected for illustration the bobbin-case comprises a cupshaped body having a cylindrical side wall I and a circular end face 2 formed with a groove 3. Located in the groove 3 is a latch 4 which is adapted to hold the bobbin-carrier in the thread basket of a rotary hook of the type illustrated in the patent to Kessler, No. 2,085,699, dated June 29, 1937.

A flat bobbin-thread tension spring, indicated generally as 5 is formed with a centrally arranged bend thereby providing two arms 6 and I. The arm 6 is secured to the cylindrical wall of the bobbin-case by a screw 8 and an adjusting screw 9 is provided for the purpose of increasing or decreasing the tension on the bobbinthread T. The free end of the arm I of the tension spring is formed with a finger Iii which extends into a circular hole II in the cylindrical bobbin-case I, The edge of the arm I of the tension spring is formed with a tang I2 which together with the finger I0 confines the bobbinthread in the slot I3 therebetween. The tang I2 is located in an open faced slot I9 formed in one end of the latch slot 3.

When the sewing machine operator wishes to replenish the lower thread, a filled bobbin I4 is inserted in the case and the operator draws the issuing end-portion of the thread sidewise into the slot I5 located in the cylindrical side wall of the case and pulls until the thread enters the aperture I6 formed in the side wall 2 and located beneath the arm I of the tension spring. A

further pull upon the thread and, at the same time, a movement of the thread to the right, as viewed in Fig. 2, causes the thread to slip sidewise under the finger It and into the thread-confining slot I3.

The thread in the position shown in Fig. 2 is the correct position for the bobbin-thread T. However, in prior constructions, because of the haste and carelessness of the operator in threading the bobbin-case, the thread is sometimes pulled so quickly and with so much force that it slips under the exposed and heretofore straight thread-confining tang I2 and therefore from under the effective end of the tension spring. To overcome this unthreading difiiculty I have formed the tang with a recess H which produces a hook-like end providing a shoulder I8 on the tang. This shoulder prevents the thread from being pulled under the tang I2 and is helped by the location of the tang in the slot I9 which is below the circular face of the thread-case and the pull of the thread and the simultaneous motion to the right causes the thread to lodge in the recess I! and lie over the shoulder I8 of the tang I2.

While the above described tension spring has been shown and described as applied to a bobbincase for use in a rotary hook it will be understood that the invention herein set forth is applicable to shuttle cases and all forms of hooks wherein the needle-thread loop is passed around a case carrying a thread-mass.

Having thus set forth the nature of the invention, what I claim herein is:

A sewing machine bobbin-case having a cupshaped body comprising a cylindrical outer wall and a circular end face, said cylindrical wall being formed with an aperture, a thread-tension leaf-spring having a shank end secured to the bobbin-case, said spring having at its free end a finger the end of which is located in the aperture in the cylindrical wall of the case, a tang on said spring and laterally spaced from said finger, said spring having a thread delivery slot between said tang and finger, and the tang being formed with a thread-catching shoulder on the edge thereof adjacent said thread-delivery slot.

DANIEL H. CHASON. 

